1. Technical Field
The present invention relates to a phosphorus-containing flame retardant epoxy resin.
2. Description of the Related Art
A reaction of an epoxy resin with a curing agent gives a three-dimensional cross-linked structure via molecular connection, ultimately obtaining a cured product having high mechanical strength and chemical resistance. The cured product of epoxy resin may be widely controlled in properties including toughness, heat resistance, water resistance, chemical resistance, weather resistance, etc., depending on the kind of curing agent. The epoxy resin having these excellent properties has been variously utilized in the field of parts of electric and electronic equipment, including semiconductor sealants, various laminates, printed circuit boards and so on. However, the epoxy resin is flammable and is thus mainly used together with a flame retardant in order to ensure combustion and fire safety.
Thus, a halogen compound containing a halogen atom in a molecule thereof (a halogen-based flame retardant) has been used to date, but is problematic because of generation of dioxin upon combustion. In order to cope with environmental concerns, a phosphorus compound containing a phosphorus atom instead of the halogen atom in a molecule thereof is being utilized these days as the flame retardant.
As the flame retardant, the phosphorus compound is known to be an additive phosphorus compound that does not react with an epoxy resin and a reactive phosphorus compound that reacts with an epoxy resin.
Examples of the additive phosphorus compound may include triphenylphosphate, tricresylphosphate, trixylenylphosphate, etc. However, since the additive phosphorus compound does not react with an epoxy resin even when added to the epoxy resin, a molded product obtained by curing the epoxy resin has problems of lowering glass-transition temperature (Tg) or deteriorating solder dip resistance after moisture absorption (see Patent Document 1).
On the other hand, an example of the reactive phosphorus compound may include 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide represented by the following formula, which is abbreviated to ┌DOPO┘, commercially available as the trade name ┌FICA┘ (hereinafter, DOPO is referred to as ┌FICA┘) (see Patent Document 2). The use of HCA is shown to solve the problem of lowering Tg of the additive phosphorus compound, and to attain high flame retardancy.
